1. Field of the Invention
The present invention relates to video processing, and, in particular, to the transmission of compressed video data between computer systems.
2. Description of the Related Art
Computer networks, such as the Internet, provide users with the ability to access multimedia information stored in computer memory devices located remotely from each user's computer. For example, a user's computer may be a personal computer (PC) system that requests and receives the multimedia information via standard analog telephone lines using a modem. One such user may request an item from an internet news service (i.e., a Web server). The item may contain one or more audio-video clips, in addition to text and still images. Typically, the audio and video streams for each clip are compressed for storage on the server's computer and eventual transmission to a user's computer. The compressed streams are then decompressed for playback upon receipt by the user's computer.
A typical 30-second video clip may be able to be compressed to about 1400 kilobytes of data. Assuming that the modem communication takes place at a conventional rate of 28.8 Kbits/sec, it would take almost six and a half minutes to transmit just the compressed video data for the clip. When the transmission of the compressed audio data is included in the calculation, the time to transmit the entire audio/video clip would be even longer. Most clips need to be played back at a real-time rate in order for the audio portion to be understandable by the user and for the video portion to be visually acceptable to the user. The limited bandwidth of conventional modems prohibits real-time playback of high-resolution, high-fidelity audio-video clips during real-time transmission of the data (i.e., with the audio/video data being decoded and rendered as they are received over the phone line). As a result, the playback of a clip is typically not started until all of the audio/video data has been received at the user's computer. This means that the user has to wait over six minutes after requesting a typical 30-second audio/video clip before the clip begins to play. This delay can be unacceptable to a user, who wants the clip to be played sooner rather than later.
Some computer systems attempt to ameliorate this problem by decoding the first frame of the 30-second video clip after that portion of the encoded video bitstream has been received and displaying the decoded first frame (for over six minutes) until the entire clip has been received at which time the clip can then be played back for real-time rendering. This does little to satisfy a user who is anxious to see the entire clip, and not just a prolonged view of the first frame.
The present invention is directed to an improved scheme for transmitting video clips between computer systems over transmission paths having limited bandwidth such as standard telephone lines.
Further objects and advantages of this invention will become apparent from the detailed description which follows.